Authorities are warning of an increasingly common scam where an anonymous email claims to have accessed a target's webcam and recorded them watching pornography.

The scam, which is strikingly similar to an episode of the popular sci-fi series Black Mirror, uses the victim's password in order to bolster its claims that the victim has been hacked.

"Lets get directly to the point. <#@$%&> is your pass word [sic.]," a sample email released by Australia's eSafety office says.

"I installed a malware on the X video clips (pornographic material) site and you know what, you visited this site to have fun (you know what I mean)."

The scam goes on to threaten that the target's webcam has been hacked, and a video of them watching the material was recorded.

"My software gathered your complete contacts from your Messenger, social networks, and e-mail account. And then I created a double video," it says.

"First part shows the video you were viewing (you have a nice taste hahah), and next part displays the view of your cam, yeah its u."

The email usually ends with a demand for hundreds or thousands of dollars in bitcoin.

So-called "sextortion scams" have been on the rise in recent years, and the eSafety office has recorded a spike in reports of the webcam scam.

"It's been around for some time, the good news is people are starting to report it," eSafety Commissioner Julie Inman Grant said.

"That's the best way we can arm people."

Valid passwords used to scare victims

The scam bears a strong resemblance to the plot of an episode of the series Black Mirror, which depicts a teenager being blackmailed into committing an increasingly serious set of crimes after his webcam was hacked to record him in a compromising position.

But according to Ms Inman Grant, the scammers had not actually accessed the victim's computer.

"What this scam does is it pulls from [a website] which reveals more than 500 million exposed passwords from previous data breaches," she said.

"While they may have guessed an old accurate password, it is very unlikely and probably close to zero that they have your intimate images.

"It's absolutely meant to panic an individual, and you can see why it would have that impact."

Victims of the scam are encouraged to never agree to demands of scammers, and never send them money.